Could anyone explain how i can find the square root of a number in c++? Is there allready a function for it? even if so i am quite interested in how the answer is found. the only way i thought of is x/n = n in a loop increasing the value of n until the expression is true but that would take ages and ages especially if the roots a decimal value. thanks.

#include <cmath.h>

functions:
float sqrt(float num);
double sqrt(double num);
long double sqrt(long double num);

this will return the square root of num, hope this helps!

Alan

it uses the fsqrt instruction

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"even if so i am quite interested in how the answer is found."
There is an ASM instruction, SQRT(?) which gives you the answer. The compiler just uses that instruction.

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Be aware that sqrt can be slow, relatively speaking. I wouldn''t use it in a tight loop.

Instead of :
if (x < sqrt (y))
...

use

if (x * x < y)
...

can anyone please explain why you do the things your suggesting? Just giving someone the code does them little good. Then they are using the code and not knowing why.

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A few methods for finding square roots may be found here. I honestly don't see, however, why the average programmer should be particularly concerned with the inner workings of whatever algorithm the processor uses for this ...


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[edited by - Miserable on January 3, 2003 8:38:21 PM]

I would have thought that the code was pretty simple to understand - call the sqrt() passing an integer/float as a parameter, the function then returns the square root of the passed int/float.

quote: Original post by Digigamer15
can anyone please explain why you do the things your suggesting? Just giving someone the code does them little good. Then they are using the code and not knowing why.\

The sqrt function is very simple and straightforward, nothing really to explain. Or are you referring to Anonomous poster''s reply about which way you should do certain operations. If so, then the reason would be because sqrt takes longer to process. Internally, it probably does alot of checks to see which two same numbers when multiplied together result in that value, which does take time. I do know that there are other mathematical ways of finding square roots without trial and error or narrowing down, but I''m unsure if C++ uses them.